U.S. patent number 5,999,409 [Application Number 09/010,184] was granted by the patent office on 1999-12-07 for contactless ic card.
This patent grant is currently assigned to Hitachi Chemical Co., Ltd., Hitachi, Ltd.. Invention is credited to Kimiaki Ando, Kazuo Kaneko, Takehiro Ohkawa.
United States Patent |
5,999,409 |
Ando , et al. |
December 7, 1999 |
Contactless IC card
Abstract
The pattern line width of a coil is partially widened in a
predetermined dimension and wiring patterns of a coil on the
surface side and a coil on the rear side are arranged so as not to
be in overlapped positions. Consequently, a direct current
resistance of the coil can be reduced and an adverse influence by a
self resonance of the coil on a communication can be reduced.
Inventors: |
Ando; Kimiaki (Hamura,
JP), Ohkawa; Takehiro (Kunitachi, JP),
Kaneko; Kazuo (Yokohama, JP) |
Assignee: |
Hitachi, Ltd. (Tokyo,
JP)
Hitachi Chemical Co., Ltd. (Tokyo, JP)
|
Family
ID: |
11839112 |
Appl.
No.: |
09/010,184 |
Filed: |
January 21, 1998 |
Foreign Application Priority Data
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Jan 28, 1997 [JP] |
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9-013650 |
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Current U.S.
Class: |
361/737; 235/492;
343/895 |
Current CPC
Class: |
G06K
19/07749 (20130101); G06K 19/07779 (20130101); G06K
19/07783 (20130101); H05K 1/16 (20130101) |
Current International
Class: |
G06K
19/077 (20060101); H05K 1/16 (20060101); H05K
001/14 (); H01Q 001/36 (); G06K 019/067 () |
Field of
Search: |
;361/728,736,737,748,794
;343/895 ;235/492 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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7-120237 |
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May 1995 |
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JP |
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8-216570 |
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Aug 1996 |
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JP |
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Primary Examiner: Picard; Leo P.
Assistant Examiner: Gandhi; Jayprakash N.
Attorney, Agent or Firm: Fay, Sharpe, Beall, Fagan, Minnich
& McKee
Claims
What is claimed is:
1. A contactless IC card comprising:
an insulating film; and
coupling areas located in central portions on front surface and a
rear surface of coil forming areas in a predetermined dimension on
the insulating film,
wherein antenna coils are formed and are constructed by a pair of
coils on the front surface and the rear surface which have turns in
the same direction when seen from the outside, are shifted by a
half pitch between a coil on the front surface and a coil on the
rear surface, and are connected via a through hole in an end part
of the coupling areas.
2. A contactless IC card comprising:
an insulating film; and
coupling areas located in central portions on a front surface and a
rear surface of coil forming areas in a predetermined dimension on
the insulating film,
wherein antenna coils constructed by a pair of coils on the front
surface and the rear surface which have turns in the same direction
when seen from the outside, are shifted by a half pitch between the
coil on the front surface and the coil on the rear surface, and are
connected via a through hole in an end part of the coupling areas
and are formed by a thick film printing method.
3. A contactless IC card comprising:
an insulating film; and
coupling areas located in central portions on a front surface and a
rear surface of coil forming areas in a predetermined dimension on
the insulating film,
wherein two or more pairs of antenna coils are formed, each
consisting of a pair of surfaces and rear coils which have turns in
the same direction when seen from the outside, being shifted by a
half pitch between the coil on the front surface and the coil on
the rear surface, and are connected via a through hole in an end
part of the coupling areas.
4. A contactless IC card having an IC circuit and an antenna coil
connected to said IC circuit, wherein said coil comprises:
a first coil portion and a second coil portion which are provided
on both surfaces of an insulating sheet opposing each other;
and
said first coil portion and said second coil portion have a first
portion and a second portion positioned in a first direction,
respectively;
said coil in said first portion and said coil in said second
portion are positioned shifted with respect to each another by a
half pitch.
5. A contactless IC card having an antenna coil, wherein:
said coil has a first coil portion and a second coil portion which
are provided on both surfaces of an insulating sheet, opposing to
each other; and
said first coil portion has a first portion and a second portion
positioned along a first and a second directions, and said second
coil portion has a third portion and a fourth portion positioned
along said first and said second directions, respectively;
wherein said coil in said first portion and said coil in said third
portion are positioned shifted with respect to each other by a half
pitch, and said coil in said second portion and said coil in said
fourth portion are positioned shifted with respect to each other by
a half pitch.
6. A contactless IC card having an antenna coil, wherein:
said coil has a first coil portion and a second coil portion which
are provided on both surfaces of an insulating sheet, opposing each
other; and
said first coil portion has a first portion and a second portion
positioned along a first and a second directions, and said second
coil portion has a third portion and a fourth portion positioned
along said first and said second directions, respectively;
said coil in said first portion and said coil in said third portion
are positioned shifted with respect to each other by a half pitch,
and said coil in said second portion and said coil in said fourth
portion are positioned shifted with respect to each other by the
half pitch;
wherein a width of said coil in said first portion is larger than a
width of said coil in said second portion, and a width of said coil
in said third portion is larger than a width of said coil in said
fourth portion.
7. A contactless IC card for transferring power and for
transmitting and receiving signals by electromagnetic coupling
between an antenna coil on a reader/writer side, comprising:
a card body of insulating material in a shape of a card;
an antenna coil on at least one of both side surfaces of said card
body;
an IC circuit mounted on a part of said card body; and
electric circuit portions on said card body for electrically
connecting at least said antenna coil and said IC circuit, wherein
said antenna coil includes conductive lines extending in one
direction on said card body and other conductive lines extending in
other direction different from the one direction, and a line width
of the conductive lines extending in the one direction is larger
than a line width of the other conductive lines extending in the
other direction.
8. A contactless IC card as defined in claim 7, wherein the one
direction is along a side edge in a lateral direction of said card
body, and the other direction is along a side edge in a vertical
direction of said card body.
9. A contactless IC card as defined in claim 7, wherein said
antenna coil is constructed with conductive paste formed on the
surface of said insulating card body.
10. A contactless IC card as defined in claim 7, further including
another antenna coil on said side surface of said insulating card
body.
11. A contactless IC card as defined in claim 7, further including
another antenna coil on another side surface of said insulating
card body opposing to the side surface on which said antenna coil
is formed.
Description
BACKGROUND OF THE INVENTION
The present invention relates to a contactless IC card for
receiving power and for receiving/transmitting signals from/to a
reader/writer as an upper terminal by electromagnetic coupling.
More particularly, the invention relates to the structure of an
antenna coil in the contactless IC card.
In recent years, attention has been paid to an IC card having
therein an IC such as a processor as a storage medium of electronic
money or the like. There are two types of IC cards according to
different signal transmitting methods. One is a contact IC card
which receives power and clocks from a reader/writer as an upper
terminal by using a contact point and processes a command from the
reader/writer. The other is a contactless IC card 32 in which, as
shown in FIG. 3, a coil 321 receives radio waves (electromagnetic
waves) generated from a reader/writer 31 through a coil 311,
transmitting and receiving data signals are generated, and a
command transmitted from the reader/writer 31 is processed.
The contactless IC card includes a contact type having the
communication distance of about few mm to 10 mm, a proximity type
having the communication distance of tens mm, and a remote type
having the communication distance of tens cm to few m. Among them,
the contact IC card has the international standard ISO10536-2 in
which the location and shape of the coils and the electric
characteristics are defined.
According to the standard ISO10536-2, as shown in FIG. 3, page 2,
ISO/IEC 10536-2:1995(E), two coils are arranged at an interval of
22 mm in a card and the inner size of the coils is defined as (11.6
mm.times.4 mm).
In order to reduce thickness, an IC card in which antenna coils are
formed by printing a conductive paste (for example, silver paste)
or the like on a PET film is used. As conventional techniques of
the IC card obtained by printing the conductive paste, there are
techniques described in Japanese Patent Application Laid-Open No.
8-216570, Japanese Patent Application No. 7-120237, and the
like.
The method of forming the antenna coil of the IC card by printing
the conductive paste (for example, a silver paste) or the like on a
PET (polyethylene terephthalate) film of the conventional
techniques have a problem that the conductance, that is, the value
of resistance of the coil is larger than that of a coil made of a
general copper wire and that of an etching coil on a printed board
by one digit or more.
Specifically, in a coil having about 20 turns, although a direct
current resistance of a coil formed by copper foil etching is 10
.OMEGA. or less, the resistance of a thick film printed coil formed
by printing the silver paste or the like is 100 to 200 .OMEGA..
When power is received and a current flows, if the direct current
resistance of the coil is large, the coil itself consumes the
power. Consequently, a loss occurs and power efficiency
deteriorates. It is therefore important to reduce the resistance of
the thick film printed coil by widening the pattern line width of
the coil as much as possible.
The coil is printed on the PET film in order to reduce the
thickness of the card in the conventional techniques. When coils
are printed on both of the surface and rear surface in order to
increase the number of turns of the coils, there is a problem such
that the antenna coils themselves have a self resonant frequency by
a floating capacity (capacitor) occurring between the coils on the
surface and rear surface and L (reactance) of the coils and an
adverse influence may be exerted on a transmission frequency band.
Specifically, the self resonant frequency by the floating capacity
when the silver paste coils each having about 20 turns are formed
on the PET film having the thickness of 50 .mu.m is few MHz to tens
MHz. Since the power and the communication frequency of the contact
IC card conforming to ISO10536 are defined as 4.91 MHz, the self
resonant frequency is a problem.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a contact IC card in
which a low-resistance antenna coil is formed by a conductive
paste.
It is another object of the invention to reduce the direct current
resistance and the floating capacity when an antenna coil in a card
is formed by using a conductive paste in a contact IC card,
especially, according to ISO10536 standard.
In order to achieve the objects, according to the first feature of
the invention, as means for reducing the direct current resistance
of the coils, means for partially widening the pattern line width
of the coil in parts having dimensional room when the coils are
formed is provided.
The second feature of the invention is realized in such a manner
that when the coils are formed in two layers on the surface and the
rear surface, as means for reducing the capacity between the coils,
the coil on the surface and the coil on the rear surface are
arranged so as not to be in overlapped positions and the wiring
pattern of the coil on the rear side is arranged between the
patterns of the coil on the surface.
The features of the invention will be more clearly described as
follows.
According to a fundamental feature of the invention, as means for
reducing the direct current resistance of the coil in a
predetermined dimension, coupling areas are formed in the central
parts on the surface and the rear surface of coil forming areas
having predetermined dimensions on an insulating film, and antenna
coils consisting of a pair of coils on the surface and the rear
surface which have the turns in the same direction when seen from
the outside and are connected via a though hole in an end part of
the coupling areas are formed by a thick film printing method.
According to the feature, the low-resistant antenna coils each
having the large number of turns can be formed in the coil forming
areas of the predetermined dimensions. Since leads of the surface
and rear surface coils formed so as to face each other on the
surface and the rear surface of the insulating film are located on
the outside of the coils, no leads traversing the coils are formed.
Both of the pair of surface and rear surface coils can be formed in
almost the same pattern and in the same winding direction on the
insulating film, so that it is advantageous also from the viewpoint
of manufacturing.
According to another feature of the invention, by forming two or
more pairs of the surface and rear coils on the insulating film,
connection between the pairs of coils (antenna coils) and external
circuits and connection between the antenna coils can be performed
on the outside of the coils.
According to another feature of the invention, in the fundamental
feature, the coil forming area is a rectangle and the line width of
the coil pattern in the longitudinal direction of the coil forming
area is formed so as to be wider. According to the feature, the
direct current resistance of the coil can be further reduced.
According to further another feature of the invention, in the
fundamental feature, the patterns of the surface and rear surface
coils of the pair of coils are formed so as to be deviated from
each other at a half pitch. According to the feature, the floating
capacity between both of the coils can be remarkably reduced.
According to the invention, in a contactless IC card in which coils
are printed by a conductive paste, the direct current resistance of
the antenna coils can be reduced and the adverse influence on the
communication by the self resonance of the coils can be reduced, so
that there is an effect that the transmission efficiency of power
and signals is improved.
The above and other objects and features of the invention will
become more apparent from the following description of the
embodiments with reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a plan view showing the shape of coils according to an
embodiment of the invention;
FIG. 2 is a diagram showing a section of a part of the coil
according to an embodiment of the invention;
FIG. 3 is a block diagram showing the circuit construction of a
contactless IC card;
FIG. 4 is a diagram showing the construction of an IC card
conforming to ISO10536;
FIG. 5 is a plan pattern diagram of two antenna coils formed by
silver paste printing;
FIG. 6 is a waveform diagram showing data transmitting and
receiving operation; and
FIG. 7 is a plan view illustrating the whole substrate of an IC
card being fabricated.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1 is a diagram showing the shape of coils of the invention.
FIG. 2 is a cross section of the coil shape of FIG. 1.
The circuit construction of a contactless IC card will be first
described.
FIG. 3 is a block diagram showing the circuit construction of the
contactless IC card. In the contactless IC card, power and signals
are transmitted and received between a coil 311 in a read/write
control circuit 31 in a reader/writer (R/W) and a coil 321 in an IC
card 32 having a communication control circuit by electromagnetic
coupling. The IC card 32 comprises: a power source circuit 322 for
generating a power voltage from an electromagnetic wave signal
received by the coil 321; a transmitting and receiving control
circuit 323 for controlling modulation/demodulation and transfer of
the transmitted and received signals; a central processing unit
(CPU) 324; and a memory 325.
An embodiment of a data transmitting/receiving method between the
read/write control circuit 31 and the IC card 32 will be described
with reference to FIG. 6.
For example, with respect to a transmitting data signal, an RS232
transmitting data signal 610 is supplied from a CPU or the like to
the read/write control circuit 31 and becomes a transmitting data
signal 601. The transmitting data signal 601 is a serial signal and
a logical signal of 0 and 1 and performs phase modulation (PSK
modulation) of 180.degree. to a carrier (4.91 MHz) signal. A PSK
modulated data signal 602 passes through a filter circuit and the
like, becomes a transmitting coil drive signal 603, and drives the
transmitting coil 311.
On the other hand, on the IC card side, a received data signal 604
is obtained by the reception coil 321 electromagnetically connected
to the coil on the transmitting side. The received data signal is
converted to a binary form data signal 605 and processes such as
demodulation are performed by the digital signal. A clock signal
606 is generated by using the binary form data signal 605 as a
reference. By sampling the binary form data signal 605 at the
leading edges of the clock signal 606, a demodulated signal 607 is
obtained.
The layout of the IC card according to the invention is as shown in
FIG. 4 so as to follow ISO10536. The IC card 32 is constructed by
an LSI 3 and coils 1 and 2. The LSI 3 has circuits 322 to 325 in
FIG. 3. The coils 1 and 2 correspond to the coil 321 in FIG. 3.
According to ISO10536, an area for transmitting and receiving
signals is determined by two coils (coils 1 and 2) arranged at an
interval of 22 mm (in the outer size of the coils) as shown in FIG.
4. The dimension of a coupling area in the coil is defined as about
11.6 mm.times.4 mm from the relation with the reader/writer.
Therefore, when the coils have to be formed in limited coil forming
areas by printing means on a card, if the number of turns of the
coil is large, it is necessary to narrow the line width of the
printing pattern.
FIG. 5 is a detailed diagram showing an example of two coils formed
by silver paste printing. Each of the coils 1 and 2 is constructed
by total 10 turns of five turns each on the surface and rear face.
A solid line A shows the pattern on the surface and a broken line B
shows the pattern on the rear face. The patterns on the surface and
the rear face are connected via a through hole at a point C on the
inner side of the coil. The silver paste coil has the pattern width
of 150 .mu.m, the thickness 20 of .mu.m, and the pattern interval
of 300 .mu.m.
Generally, since the conductance of the silver paste coil is
smaller than that of an etching coil or a winding coil by 10 to 20
times, there may be a problem of an impedance (internal
resistance).
That is, when the pattern width of the printed coil is narrowed,
the impedance (resistance) of the coil increases and the power is
not easily obtained. Especially, when a conductive paste such as
silver paste is used, the value of resistance in case of a coil
having 20 turns and the line width of 150 .mu.m is around 200
.OMEGA. and large, which is much larger than that of the etching
coil. The internal resistance of the coil is a loss when the power
is obtained. When the consuming current of the IC card on which a
CPU is mounted is, for example, about 3 V/10 mA, the power is 30
mW, and the loss by the coil is 20 mW. It is an order which cannot
be ignored.
FIG. 1 is a diagram showing a preferred embodiment of the
invention. In FIG. 1, wiring t1 in the vertical direction of the
antenna coils 1 and 2 having the coupling areas in the center has
the line width of 150 .mu.m same as that of FIG. 5 and the wiring
line width t2 in the lateral direction is 300 .mu.m which is wider
than t1. When the pattern in the vertical direction along the short
side of the rectangular coupling area cannot be widened, because if
it is widened, the coils 1 and 2 are short-circuited. The pattern
in the lateral direction has dimensional room in the ISO standard
and can be widened. The widths of the patterns in the vertical and
lateral directions are varied as mentioned above, thereby enabling
the impedance of the whole antenna coils to be further reduced.
FIG. 2 is a cross sectional view taken on line X-Y of the antenna
coil 2 in FIG. 1. Reference numeral 201 denotes a PET film having
the thickness of 50 .mu.m; 202 a silver paste printed coil on the
surface; and 203 a silver paste printed coil on the rear face. In
case of the printed coil using the PET film, the thickness of the
film is thinner than that in case of performing an etching to a
general substrate, so that a large floating capacity occurs. When
the coil wiring on the surface and rear face are arranged in facing
positions, the floating capacity occurs between the wiring on the
surface and that on the rear face, and the floating capacity and
the coil form a resonant circuit. When the resonant frequency is
almost equal to the communication frequency, an adverse influence
is exerted.
According to experiments, the self resonant frequency in case of
the above coil construction lies in a range from few MHz to tens
MHz The communication frequency of the power and signals of the
contact IC card according to ISO10536 is defined as 4.91 MHz, so
that the self resonant frequency is a problem.
FIG. 2 shows the antenna coil constructed so as to reduce the
influence of the floating capacity. As shown in the diagram, in
order to reduce the floating capacity occurring between the coils
on the surface and the rear surface, the coil on the surface and
the coil on the rear face are arranged to deviate from each other
at a 1/2 pitch so as not to be in overlapped positions. The wiring
pattern 203 of the coil on the rear side is arranged between the
wiring of the coil pattern 202 on the surface.
FIG. 7 is a diagram showing the whole substrate (PET film
substrate) of the IC card employing the invention. The dimension in
the lateral direction of the antenna coils 1 and 2 is larger than
that in the vertical direction. An integrated circuit is mounted in
a position shown by 3. Further, a terminal 701 is a test terminal
for a circuit debug and is cut when the IC card is completed.
* * * * *